The present invention relates to an evaporated fuel piping construction for a vehicular engine which supports a purge pipe member.
In vehicles, evaporated fuel leaking to the atmosphere from a fuel tank or the like contains hydro carbons (HC) in large quantities, which is responsible partly for air pollution and leads to loss of fuel. There are known various techniques for prevention of air pollution and loss of fuel. As a typical one, there is an evaporated fuel control device (evaporative system) in which evaporated fuel in a fuel tank is absorbed by an absorbent material, such as activated charcoal, and is purged at the time of engine operation. Purge air including purged evaporated fuel is fed to the engine.
In a known piping construction for the evaporated fuel control device as shown in FIG. 10, a purge pipe member 106 is provided between a canister 102 and a throttle body 104, which is a part in an intake system, to conduct evaporated fuel from the canister 102 to the throttle body 104. The purge pipe member 106 is made-of a flexible hose, and is connected at its one end to a purge side union 108 of the canister 102, fixed at its middle portion to a vehicle body by a plurality of hose mounting clamps 110, and connected to a body side union 112 of the throttle body 104.
Such evaporated fuel piping constructions are disclosed in, for example, Japanese Patent Laid-Open Nos. 286563/1995 and 61161/1996. With the arrangement described in Japanese Patent Laid-Open No. 286563/1995, a metallic pipe is provided midway of a purge pipe member and is fixed to an engine side through a bracket together with parts such as a purge valve and the-like to suppress transmission of air current sound through the purge passage. With the arrangement described in Japanese Patent Laid-Open Nos. 61161/1996, a surge tank is provided on a purge pipe member between an intake manifold and a purge valve to flatten fluctuation in the amount of purge.
In conventional evaporated fuel piping constructions, a plurality of hose mounting clamps are mounted to a lengthy flexible hose as a purge pipe member and mounted to a vehicle body to then be connected to a throttle body as shown in FIG. 10, there is a disadvantage in that a piping path for the purge pipe member becomes too long to lack invariability or to control the position thereof. Thus, it becomes difficult to ensure clearances between the path and other adjacent parts, and a large sag is needed in the hose due to the hose being directed in a direction V (FIG. 10) perpendicular to a direction C of an engine crankshaft axis.
To eliminate or minimize the above described disadvantage, the invention provides an evaporated fuel piping construction for a vehicular engine, including a purge pipe member provided between a canister and an intake system to conduct evaporated fuel from the canister to the intake system. The purge pipe member comprises a non-flexible pipe member or members fixed to an engine accessory and a flexible pipe member or members connected to the non-flexible pipe member or members.
In the invention, the non-flexible pipe member or members, which constitute a part of the purge pipe member, are fixed to an engine accessory, and a flexible pipe member or members form the remaining part of the purge pipe member, so that it is possible to shorten the piping path for improvement in invariability, to provide substantially predetermined placement of the flexible pipe members relative to other elements of the engine, to ensure adequate clearances between the purge pipe members and other parts and to make the flexible pipe members of the purge pipe members small in sag or in the amount of free movement of the flexible pipe members.